package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import javax.sql.DataSource;
import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * @author: xiangfeng
 * @date: 2021年09月29日
 */

public class SimpleExecutor implements Executor {

    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        PreparedStatement preparedStatement = executeSql(configuration, mappedStatement, params[0]);

        //5.执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        List<Object> objects = new ArrayList<>();
        //6.封装返回结果集
        while (resultSet.next()){//一条一条进行遍历
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段的值
                Object value = resultSet.getObject(columnName);
                //使用内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            objects.add(o);
        }
        return (List<E>) objects;
    }

    @Override
    public void update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws ClassNotFoundException, SQLException, IllegalAccessException, NoSuchFieldException {
        PreparedStatement preparedStatement = executeSql(configuration, mappedStatement, params[0]);
        preparedStatement.execute();
    }

    private PreparedStatement executeSql(Configuration configuration, MappedStatement mappedStatement, Object param) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
        //1.注册驱动,获取连接
        Connection connection = configuration.getDataSource().getConnection();
        //2.获取sql语句:select * from user where id=#{id} and username=#{username}
        //  转换sql语句：select * from user where id=? and username=?,
        //     转换过程中，还需要对#{}里面的值进行存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql =  getBoundSql(sql);

        //3.获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4.设置参数
        //4.1 获取参数全路径
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);

        List<ParameterMapping> parameterMappingListList = boundSql.getParameterMappingListList();
        for (int i = 0; i < parameterMappingListList.size(); i++) {//若没有参数，则不进入该循环
            ParameterMapping parameterMapping = parameterMappingListList.get(i);
            String content = parameterMapping.getContent();
            //反射
            Field declaredField = parameterTypeClass.getDeclaredField(content);
            //暴力破解
            declaredField.setAccessible(true);
            Object o = declaredField.get(param);
            preparedStatement.setObject(i+1,o);
        }
        return preparedStatement;
    }



    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if(parameterType!=null){
            Class<?> aClass = Class.forName(parameterType);
            return aClass;
        }
        return null;
    }

    /**
     * 对#{}解析：1.将#{}使用？进行代替  2.解析出#{}里面的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配合标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        //标记解析器
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        return new BoundSql(parseSql,parameterMappings);
    }
}
